Orientation and rate dependence in high strain-rate compression of single-crystal silicon

High strain-rate ((epsilon)over dot similar to 10(6)-10(9) s(-1)) compression of single crystal Si reveals strong orientation- and rate-dependent precursor stresses. At these high compression rates, the peak elastic stress, sigma(E_Peak), for Si [100], [110], and [111] exceeds twice the Hugoniot elastic limit. Near the loading surface, the rate at which Si evolves from uniaxial compression to a three-dimensional relaxed state is exponentially dependent on sigma(E_Peak) and independent of initial crystal orientation. At later times, the high elastic wave speed results in a temporal decoupling of the elastic precursor from the main inelastic wave. A rapid high-(epsilon)over dot increase in the measured elastic stress at the onset of inelastic deformation is consistent with a transition from dislocation flow mediated by thermal activation to a phonon drag regime. DOI: 10.1103/PhysRevB.86.245204